The invention disclosed herein pertains to a lifting and swivelling device for a cover of a furnace, and more particularly to a lifting and swivelling device for a cover of an arc furnace.
During the charging of a furnace all parts of the furnace located above a cauldron of the furnace, including a cover and a superstructure of the furnace, are temporarily moved to one side of the cauldron. After having been moved aside there is a danger that the cover and the superstructure may be unintentionally lowered.
Accordingly, a primary object of the present invention is to provide a method and apparatus for moving a cover and a superstructure of a furnace away from a cauldron of the furnace, while preventing an unintentional lowering of the cover and the superstructure after they have been moved away from the cauldron of the furnace.
Apparatus according to the present invention for moving a cover and a superstructure of a furnace away from a cauldron of the furnace includes a rotatable column arranged adjacent the cauldron of the furnace. The rotatable column is used to lift the superstructure of the furnace above the cauldron, and is used to swivel the superstructure and the cover away from the cauldron.
The lifting of the superstructure is accomplished hydraulically. That is, in a first embodiment of the present invention the rotatable column is itself a piston of an hydraulic cylinder. In a second embodiment a separate hydraulic apparatus for exerting an upward lifting force against a bottom of the rotatable column is arranged beneath the column.
The column may be rotated in one of two ways. That is, in a third embodiment of the present invention, a first toothed segment engages a second toothed segment connected to the column. In a fourth embodiment of the present invention, which is a preferred embodiment, a first end of a double-acting hydraulic cylinder is connected to a stationary stand of a swivelling apparatus, while a second end of the double-acting hydraulic cylinder is connected, at a tangent, to the rotatable column by a lever.
In the preferred embodiment of apparatus, according to the present invention, the apparatus for lifting the superstructure and cover of a furnace and for swivelling the cover, which apparatus includes a column, rests firmly on a foundation of the furnace. The superstructure of the furnace tilts with the cauldron of the furnace during pouring and slagging off operations. Thus the lifting and swivelling apparatus must be capable of being coupled to the superstructure of the furnace during a lifting and swivelling operation, and of being disengaged from the superstructure during a tilting operation such as a pouring or slagging off operation. To accomplish these functions the preferred embodiment of apparatus includes a rotatable column having a conically shaped upper end, which conically shaped upper end may be inserted into a corresponding conically shaped receiving aperture or bore in the superstructure.
The preferred embodiment of apparatus, according to the present invention, is advantageous because the conical shapes of the upper end of the rotatable column and of the corresponding receiving bore in the superstructure ensure that the rotatable column will move safely into the receiving bore, even if there is some slight eccentricity in the shape of the bore or the shape of the upper end of the column.
The preferred embodiment of the present invention also includes a cylinder within which the rotatable column moves, and guides which are connected to an interior of the cylinder and which ensure that the column moves only in a vertical direction. In addition, the preferred embodiment also includes a bar, which may be cylindrical in shape, which bar is spaced apart from, but rigidly connected to, the column. A swivelling apparatus engages the bar to thereby rotate the column. Further, a plate having an aperture through which the bar may pass is rigidly connected to the cylinder. The aperture in the plate is arranged so that when the column is moved vertically upward or downward the bar may pass through the aperture, but after the bar is moved by the swivelling device to rotate the column the bar is out of alignment with the aperture and is thus prevented from moving in the vertical direction. Consequently, the column is prevented from moving in the vertical direction.
The preferred embodiment is also advantageous because the cylindrical bar in combination with the apertured plate greatly reduces the possibility that a superstructure and cover of a furnace which have been raised and swung away from a cauldron might be inadvertently lowered. Thus the stability of the superstructure is enhanced and the possibility of jamming the column's guides is reduced.
In the preferred embodiment the bar, rather than the column, is connected to, and engaged by, the swivelling apparatus. The bar need not be an additional element to the present invention because a driving pin of the swivelling apparatus, which swivelling apparatus is, in any event, needed to rotate the column, may be used as the bar. A length of the driving pin need only be extended by a length of an upstroke of the rotatable column.
The swivelling apparatus used to engage the cylindrical bar, in the preferred embodiment of the present invention, includes a swivelling cylinder. In addition, the swivelling apparatus is mounted on the apertured plate which is connected to the cylinder. Thus, no additional parts are needed to support the swivelling apparatus.
The preferred embodiment of the present invention further includes a stop which substantially confines a motion of the swivelling apparatus to a horizontal plane and largely prevents the swivelling apparatus from undergoing a vertical motion. That is, the stop confines a motion of the swivelling apparatus to a plane which is substantially perpendicular to a longitudinal axis of the column. This is an advantageous feature of the preferred embodiment because without the stop the swivelling apparatus might be frictionally carried along by the bar in a vertical direction during a vertical movement of the bar, resulting in the swivelling apparatus assuming an inclined position. Such an inclined position could cause an undesired rotation of the rotatable column and of the superstructure of the furnace.
In the preferred embodiment of the present invention the cylindrical bar includes a support piece connected to a bottom end of the bar, which support piece has a horizontal cross-section larger than that of the bar. This support piece aids in maintaining the swivelling apparatus in a proper position during a swivelling movement. The support piece also aids in maintaining the swivelling device in a proper position after the cover and the superstructure of a furnace have been swung away from a cauldron of the furnace. Further, because a horizontal cross-section of the support piece is greater than a horizontal cross-section of the bar, the bar is protected from mechanical damage during its movement through the aperture in the apertured plate connected to the cylinder. In addition, the surface of the bar remains smooth and a mutual movement of the bar and of a pivot head of the swivelling apparatus is thus facilitated.
The preferred embodiment of the present invention further includes one or more guide plates which are arranged beneath the apertured plate connected to the cylinder. Each of these plates is arranged so as to be tangent to a point on an outer perimeter of the aperture in the apertured plate. These guide plates are advantageous because they guide the support piece connected to the lower end of the cylindrical bar when the bar is beneath the apertured plate so that the smooth surface of the bar does not touch the wall of the apertured plate and thus is not damaged.